杞人忧天groundless fears (lit. man of Qǐ fears the sky falling)

七上八下uneasiness;in a mess

齐心协力to work with a common purpose;to make concerted efforts;to pull together;to work as one

岂有此理how can this be so?;preposterous;ridiculous;absurd

恰到好处it’s just perfect;it’s just right

千差万别unlike any other;different

千方百计a hundred plans;by every possible means (lit. thousand ways)

千钧一发in imminent peril;extremely delicate situation;extremely critical moment

黔驴技穷sb. who has exposed his limited ability;to exhaust one’s limited abilities

千丝万缕countless ties;a thousand and one links;interrelated in innumerable ways